Blower wheel blade construction and method of assembly



May 28, 1963 V. N. DELANEY BLOWER WHEEL BLADE CONSTRUCTION AND METHOD OF ASSEMBLY Filed March 17, 1960 2 Sheets-Sheet 1 INVENTOR V/NCENTMD ELANEV ATTORNEYS May 28, 1963 v. N. DELANEY BLOWER WHEEL BLADE CONSTRUCTION AND METHOD OF ASSEMBLY 2 Sheets-Sheet 2 Filed March 1'7, 1960 United States Patent 3,091,384 BLOWER WHEEL BLADE CONSTRUCTION AND METHOD OF ASSEMBLY Vincent N. Delaney, Torrington, Conn, assignor to The Torrington Manufacturing Company, Torrington, Conn., a corporation of Connecticut Filed Mar. 17, 1960, Ser. No. 15,688 12 Claims. (Cl. 230134) This invention relates to blower wheels of the type having an annular series of longitudinal air moving blades, and deals more particularly with a blade construction and method of assembly whereby the individual blades are interlinked to form a chain of blades requiring only the addition of support members to complete the blower wheel.

The general object of this invention is to provide an improved blower wheel construction and method of assembly which substantially reduce the time and labor required to make a complete blower wheel by eliminating the usual necessity of separately fastening each blade to the blade supporting members.

A more specific object of this invention is to provide a blower wheel construction employing blades that may be rapidly formed from a strip of sheet material and linked together in a multi-station press to provide a flexible chain of blades requiring only the addition of support members to complete the wheel.

Another object of this invention is to provide a method of forming a chain of interlinked blades from a strip of sheet material, the steps of which method, including the interlinking of the blades, may be readily carried out in a multi-station press so as to require no hand operation.

Further objects and advantages will be apparent from the drawings and the following description and claims.

The drawings show in detail the preferred embodiment of the invention and such embodiment will be described,

7 but it will be understood that various changes may be made from the construction and method shown, and that the description and drawings are not to be construed as defining or limiting the scope of the invention, the claims forming a part of this specification being relied upon for that purpose.

Of the drawings:

FIG. 1 is a plan view of a sheet of material illustrating the various operations performed thereon in accordanw with this invention to produce a chain of interlinked blades,

FIG. 2 is an end view of the sheet material shown in FIG. 1,

FIG. 3 is a vertical sectional view taken on the line 3--3 of FIG. 1,

FIG. 4 is an enlarged plan view of the end portion of a blade made by the process shown in FIG. 1,

FIG. 5 is an end view of the blade portion shown in FIG. 4,

FIG. 6 is a side view of the blade portion shown in FIG. 4,

FIG. 7 is an enlarged plan view showing the ends of several interlinked blades made by the process shown in FIG. 1,

FIG. 8 is an end view of the blades shown in FIG. 7,

FIG. 9 is a partial end view of a blower Wheel employing blades made in accordance with this invention, and

FIG. 10 is a vertical sectional view taken on the line 1010 of FIG. 9.

In practicing the method of this invention, it is preferred, but not essential, that the blades be formed, as shown in FIGS. 1 and 2, from a strip of sheet material which is cut at one point in the blade forming process along the transverse lines a, a to separate the blades from 3,091,384 Patented May 28, 1963 the strip. The lines a, a thus divide the strip 20 into rectangular blanks 22, 22 from each of which blanks a single blade is made. The blanks, of course, are integrally connected one to another in the strip, and the dividing lines a, a are imaginary or invisible until such time as the blanks are sheared from the strip. The steps involved in making blades from the strip 20 are best carried out in a multi-station press equipped with various metal forming and cutting dies, and the method will be described as though carried out by the use of such a press. It will be understood, however, that the invention is not limited to the use of a press and that the invention may be practiced by the use of other conventional metal forming tools.

Referring to FIGS. 1 and 2, the metal strip 20 is fed into the press (not shown) where it is first pierced to provide holes 24, 24 and slits 26, 26 along each edge of the strip, the holes 24 and the slits 26 being formed at regularly spaced intervals so that one hole and one slit are located at each end of each rectangular blank 22. The holes '24, 24 form no part of the completed blades, but serve as piloting holes for positively locating the strip 20 in the press and for maintaining a uniform spacing between the lines a, a. That is, the holes 24, 24 receive pilot members of the press which hold the strip 20 during the press cycles and accurately locate it relative to the press stations. In the description which follows, the stations at which the succeeding operations are performed on the strip '20 are indicated generally in FIGS. 1 and 2 by the letters A to H inclusive. Between cycles of the press the strip is advanced to the left a distance equal to the spacing between the lines a, a so as to move each blank 22 progressively through the stations A to H. The sequence of operations performed on each blank 22 may therefore be described by taking up in sequence the sta tions A to H and considering the operations performed at each. This form of description will be followed below, and to simplify the same it will be assumed that the same blank 22 is operated upon at each station.

At the station A which follows the piercing operation described above, portions of each end of the rectangular blank 22 are cut away by a blanking die to produce end shapes 2%, 28, leaving between the end shapes 28, 28 a solid middle portion or body 30 Which later becomes the body of the finished blade. The blanking operation which produces the end shapes 28, 28 also produces a notch 32 in each end of the body 3%, and smaller notches 3'4, 34 adjacent the lines a, a along which the sheet 20 is later out. In addition, the center of the strip 20 may be pierced at the station A to provide a trapezoidal opening 35 adjacent the middle of each dividing line a. This opening, as will later be described, provides a notch in each fiinished blade for fastening the blade to the particular hub structure disclosed herein. For diflerent hub structures, however, the opening 35 may be of a different shape than that shown, or may be omitted entirely. Also, the piercing operation which provides the opening 35 need not be performed at the station A, but may be performed at another succeeding station if desired.

At the next station of the press, indicated at B, each of the end shapes 28, 28 of the blank 22 is bent adjacent its rear portion at angles along two bend lines to produce an offset portion 36 and a foot portion 38. The offset portion 36, as seen best in FIG. 2, extends perpendicularly, and in this case downwardly, from the plane of the sheet 20 while the foot portion 38, which is formed along the lower edge of the offset portion, is parallel to the sheet 20. The lines along which the bending occurs in this operation are preferably slightly arcuate so that the resulting offset and foot portions will also be slightly arcuate in shape. As will be evident later, the degree of arcuate curvature of the offset and foot portions depends n the size of wheel in which the blades are used. In the completed wheel the offset and foot portions of the several blades collectively define annuli at the ends of the wheel, and therefore, these portions should preferably have radii of curvature substantially equal to the radii of these annuli.

After the'bending operation at station B, which forms an offset portion 36 and a foot portion 38 on each end shape .28, the end shapes are trimmed adjacent the forward sides thereof by a further cutting or blanking operation, at the station C, to define tab portions 49, 40 each having a notch 42 in its forward edge, with the sides of the notch being defined by two spaced and outwardly projecting fingers 43, 43. The slits 26, 26 are elongated in this operation and define the inner side edges of the tab portions 40, 40. The tab portions 40, 40 are then, at station D, bent 90 in the opposite direction from the ofiset portions 36, 36 so as to extend perpendicularly, and in this case upwardly, from the plane of the sheet 20, with each tab portion being disposed in substantially the same plane as its associated offset portion 36.

Next, at the station indicated at E, each of the end shapes 28 of the blank 22 are bent upwardly from the plane of the blank or sheet material 20 along a bend line 7 adjacent the end of the body 30. During this operation a gusset 44 is, or may be, formed between each end shape and the body by pressing the sheet material inwardly along a line at right angles to the bend line between the body and the end shape. The bending of the end shapes relative to the body 30 brings the tab portions 40, 40 to positions whereat the notches 42, 42 therein face generally inwardly toward one another. The end shapes in this operation are preferably each bent by an angle somewhat less than 90 so as to diverge outwardly from .the ends of the associated body 3%. The tabs 40, 40 are of such length that after the bending of the end shapes, the ends of the fingers 43, 43 on the opposed tabs are spaced apart by a distance greater than the distance between the bases of the opposed notches 32, 32 in the body 30. The particular angle to which the end shapes 28, 28 are bent is not critical so long as the spacing between the ends of the opposed fingers 43, 43 is greater than the spacing between the body notches 32, 32. It is preferred to bend each end shape of the blade by an equal angle, as shown and described, but this is not necessary. One of the end shapes may, for example, be bent to a 90 angle relative to the body 30 and the other end shape bent to an angle substantially less .than 90 provided the required spacing between the tabs is main- .tained in so doing. Also, at this point in the blade-forming process-the end shapes 28, 28 of the blank lose their character as such and become, and will be referred to hereafter as flanges-46, 46, each having on its outer-end anofiset portion 36, a foot portion 38, and a tab 40.

After being operated on at station E, the sheet material 20 is cut or lanced along the transverse line a, .at stationF, to separate the blank 22 from the sheet. -As a result of this shearing operation, the respective openings 35 define notches 50 midway between the ends of the corresponding separated blank,.each notch Stlbeing located in the right-hand edge of the blank, as shown in FIG. 1, and having inwardlydiverging edges52, 52. Afterthe blank is :cut from the sheet at F, it is transferred to the station G where the body portion 30 of the blank, which is flatup to this point, as shown by the broken lines at station G in FIG. 2, is bent or shaped to form an arcuate cross-section, as shown by the solid lines at station G in FIG. 2, and to convert the blank into a finished blade 54.

Theconstruction of the finished blade 54, after the shaping operation at the station G, is best shown-in the enlarged views of FIGS. 3 to 6, inclusive, and will be summarized below. As shown in these figures, the blade ;54'includes a longitudinal body 30 which is arcuate in transverse cross-section. At each end of the body 30 is a flange 46 which extends upwardly from the body and which diverges somewhat outwardly from the end thereof, as shown best in FIG. 6. A gusset 44 is formed between the flange 46 and the body 30 to strengthen the bend between the latter two members. On the outer part of each flange 46 is an offset portion '36 which extends generally outwardly from the end of the body 30, a foot portion 38 which extends generally upwardly from the outer edge of the offset portion, and a tab .40 which extends generally inwardly toward the body 30. The tab 40 includes two inwardly directed fingers 43, 43 which are spaced apart and define a notch 42 in the inner end of the tab. Rearwardly, or to the right of the flange 46, as viewed in FIGS. 4 and 5,t.he blade 54 has a notch 32 formed in the end of the body 30, which notch opens axially outwardly, as shown in FIG. 4.

Each finished blade 54 produced at the station G is thereafter connected to the next preceding blade to produce a flexible chain of interlinked blades. This is, or may be, accomplished as shown in FIGS. '1 and 2 by transferring the finished blade 54 from the station G to the station H and positioning it at the latter station so that the inwardly opening notches 42, 42 in the opposed tabs 40, 40 thereof straddle the outwardly opening notches 32, 32 in the next preceding blade 54. Then at least one ofthe flanges 46, 46 of the finished'blade is bent inwardly a further distance toward the body 30 to decrease the spacing between the tabs 40, 40 and to thereby bring the tab notches 42, 42. into interfitting relationship with the body notches of the preceding blade and in which relationship the spaced fingers 43, 13 of each tab lie .on opposite sides of the body of the preceding blade and the bases of the tab notches are substantially in engagement with the corresponding bases of the body notches. The finished blade is thus free to pivot to a limited extent about the axis of its tab notches, but is restrained against axial and lateral movement, as ,willbe evident from FIGS. 1 and'2. As mentioned previously, it is preferred that the flanges 46, 46, prior to the bending operation at stationH, diverge outwardly from theends of he body 30'by substantially equal angles; anditfisfnrther preferred, as shown infElGS. 1 and 2, that at the station H'the two. flanges 46, 46 each be bent substantially the same additional amount andthat the final angle between each flange and its body be approximately 90, although this is not essential to -thebroader aspects of the invention.

A chain of several. interlinked blades 54,54, as they leave the press,.is shown at the left of FIGS, 1 and 2 and indicated in general by the reference numeral 56. Anthe station H each finishedblade 54 is,in turn connected to the last blade in the chain '56, the finished blade ,then becoming the last blade inathe chain to which thenext finished blade is connected. After each new blade, is

. added to the chain the .latter is advanced forward or to the left, to make room forthenextblade to beadded. .The chain of interlinkedblades which tln s emerges from the press may thereafter be broken into usable lengths by counting off a desirednumber of blades andjthen spreading apart one or both of'the tabs of the proper blade to free the preceding blade. This operationmay be done'by hand, but is preferably accomplished by a suitable counting and spreading mechanism located at-the discharge end of the press. Alternatively, the chain 56 could also be divided into usable lengths byomitting the relationship between the body notches 32, 32 of one blade and the tab notches 42, 42 of the adjacent blade on the right. The two fingers of each tab 40 are disposed on opposite sides of the associated blade body, and the base of each tab notch 42 engages, or substantially engages, the base of the associated body notch 32 so that the blades are restrained against relative displacement other than a limited pivotal movement about the axis of the notches. This limited pivotal movement between adjacent blades makes the chain flexible so that if a suflicient number of blades are in a given length of chain the latter may be closed upon itself and made into a continuous annular member by positioning the body notches 32, 32 of the last blade between the spread apart tab notches 42, 42 of the first blade and then bending the flanges 46, 46 of the first blade inwardly to connect the blades. This step, however, is usually not performed until the chain is first positioned around a suitable hub structure, as described below.

A blower wheel 58 employing a series of interlinked blades 54, 54 as described above is shown in FIGS. 9 and 10. In addition to the blades, the wheel 58 includes a hub structure 60 and two end rings 62, 62. Both the hub structure and the two end rings shown in these figures are similar to the corresponding structures shown in the application of Kenneth A. Merz, Serial No. 548,166, filed November 21, 1955, now Patent No. 3,004,326, to which reference is made for a detailed description of these elements and the method in which the blades are fastened to the hub structure. It should be understood, however, that the structure illustrated herein for supporting the blades is exemplary only and that other structures which serve to support the blades as a rigid unit adapted for rotation about a central axis may be employed.

Briefly, the hub structure includes two annular discs 64, 64 each having its inner portion connected to a hub member 66, an outer peripheral portion 68, and an annular bead 70 adjacent and spaced inwardly from the peripheral portion. In making the wheel 58 a length of chain 56 having the proper number of blades 54, 54 is positioned around the periphery of the hub structure, as shown in FIG. 9, with the longitudinal axes of the blades parallel to the central axis of the hub structure about which the hub members 66, 66 rotate. In positioning the chain of blades around the hub structure, the peripheral portions 68, 68 of the discs 64, 64 are entered into the notches 50, 50 of the blades. Thereafter, the peripheral portions 68, 68 are bent outwardly into engagement with the side edges 52, 52 of the notches 50, 50, as shown in FIG. 10, to connect each blade in fixed relationship to the hub structure, by pressing together the two beads 70, 70.

As shown in FIG. 9, the blades 54, 54, after their attachment to the hub structure, form an annular series around the hub axis with the opposite ends of the blades disposed respectively in two axially spaced planes, FIG.

' 10. The flange 46 on each end of each blade 54 extends tween adjacent blades prevents each blade from moving axially or circumferentially. The ofiset portion 36 and the foot portion 38 on each flange are preferably of such circumferential length and so oriented that, as shown in FIG. 9, the individual'offset and foot portions at each end of the wheel 58 collectively define a substantially continuous oflset annulus 72 and a substantially continuous foot annulus 74 at each end of the wheel to which annuli the end rings 62, 62 may be attached, as shown in FIG. 9, by a spinning operation. The end rings 62, 62 maintain the ends of the blades in the rigid annular relationship shown and together with the hub structure 60 form the blades into a completed wheel.

In FIG. 9 the preferred direction of rotation for the illustrated blower wheel is shown, as indicated by the arrow, to be in the counterclockwise sense, and in the above description and the claims the terms forward and rearward have been used with this direction of rotation in mind, although in actual use the blower wheel may in some instances be rotated in the opposite direction.

The invention claimed is:

1. A blower wheel of the centrifugal type comprising, a hub structure rotatable about a central axis, a plurality of longitudinal lair moving blades rotatable with said hub structure, said blades being arranged in an annular series about said hub structure with the longitudinal axes thereof generally parallel to said central axis and with the opposite ends of said blades disposed respectively in two axially spaced radial planes, a flange on each end of each blade extending forwardly and radially outwardly with respect to the associated blade, means defining an axially outwardly opening notch in each end of each blade rearwardly of the associated flange, and an axially inwardly directed tab on the forward portion of each of said flanges, each of said tabs having an axially inwardly opening notch in the inner end thereof which engages in interfitting relationship the notch in the corresponding end of the next adjacent blade to link together adjacent blades and prevent relative circumferential and axial displacement therebetween.

2. A blower wheel of the centrifugal type comprising, a hub structure rotatable around a central axis, a plurality of longitudinal air moving blades rotatable with said hub structure, said blades being arranged in an annular series about said hub structure with the longitudinal axes thereof generally parallel to said central axis and with the opposite ends of said blades disposed respectively in two axially spaced radial planes, a flange .on each end of each blade extending forwardly and radially outwardly with respect to the associated blade, means defining an axially outwardly opening notch in each end of each blade rearwardly of the associated flange, and an axially inwardly directed tab on the forward portion of each of said flanges, each of said tabs having two axially inwardly directed and circumferentially spaced fingers on the inner end thereof and an axially inwardly opening notch defined between the two said fingers, the notch of each tab being interfitted with the notch in the corresponding end of the next adjacent blade with the two fingers of the tab being disposed on opposite sides of the blade and extending axially inwardly beyond the base of the blade end notch to engage the blade and prevent circumferential movement thereof relative to the tab.

3. A blower wheel of the centrifugal type comprising, a hub structure rotatable about a central axis, a plurality of longitudinal air moving blades rotatable with said hub structure, said blades being arranged in an annular series about said hub structure with the longitudinal axes thereof generally parallel to said central axis and with the opposite ends of said blades disposed respectively in two axially spaced radial planes, a flange on each end of each blade extending forwardly and radially outwardly with respect to the associated blade, means defining an axially outwardly opening notch in each end of each blade rearwardly of the associated flange, a circumferentially elongated offset portion on each of said flanges and extending axially outwardly therefrom, a tab extending axially inwardly from the forward end of each of said offset portions, each of said tabs having an axially inwardly opening notch in the inner end thereof which engages in interfitting relationship the notch in the corresponding end of the next adjacent blade to link together adjacent blades and prevent relative circumferential and axial displacement therebetween, a radially outwardly extending foot portion formed along the outer edge of each of said offset portions, said offset and said foot portions being of such length and so oriented 'as to collectively define substantially continuous offset and foot annuli at each end of said blower wheel, and a ring at each end of said blower wheel connected to the annuli defined by the corterial toleave a body portion pond n of se a d oo ort pn to h ai latter portions in their annular relationship.

A cha n f int rl k b ad s q u e in ab n a blower wheel of the centrifugal type, said chain conr prising a plurality of elongated blades of arcuate crosse t n ar an i laterally s ac r la ions w their longitudinal axes parallel, each of said blades having an axially outwardly opening notch in each end thereof intermediate its side edges, 'a flange on each end of each blade extendingaway from the associated blade a plane generally perpendicnlarto the longitudinal axis thereof, and a tab earriedby each of said flanges'and having an axially inwardlyopening notch therein, the notches in thetwo tabs of each blade engaging respectively "the notches in the twoends of the nextadjacent blade to link together the adjacent blades.

6. A chain of interlinked blades for use in fabricating a blower wheel of the centrifugal type, said chain comprising a plurality of elongated blades of larcuatecrosssection arrangedin laterally spaced relation withtheir longitudinal axes parallel, each of said blades having an H axially outwardly opening notch in each end thereof intermediate its side edges, a flange on each end of each bladeextending ,away from the associated blade in a plane generally perpendicular to the longitudinal axis thereof, each of said flanges carrying an offset portion extending axially outwardly therefrom and a foot por- -tion formed along the outer edge of said offset portion, said offset ,and footv portions being elongated and arcuate ina plane perpendicular to the longitudinal axis of the associated blade, vand a tab carried by each of said flanges ,and.having an axially inwardly opening notch therein, thenotches in ,the two. ends of each blade interfitting respectively with the notches in the two ends of the next adjacent blade to,pivotally link together the adjacent b d s- ;6. -A chain of interlinked blades for use in fabricating ablowerwheel. of the centrifugal type, said chain comprising a plurality of blades, each of said blades having abody portion .of varcuate cross-section and a pair of flanges extendingone from each end of said body portion, said body portion having a pair of axially outwardly opening notches therein located one oneach end of said ,body portion and said flanges each having an inwardly directed tab withan inwardly opening notch therein, all except the, firstof said blades having the flanges thereof disposed in planes substantially perpendicular to thebody spontion of said blades withthe tabs ofone blade receivjingthe body portion, of the next adjacent blade and with ;the-notch es of the tabs beinginterfitted with the notches heflbody portion to. pivotally connect the blades, the ngesof said first bladefliverging outwardly from the vibody portion thereof so as to be capable of receiving. the

- body portion ,of-another {blade betweenits tabs without interference. i

'7. fIl'lC'mQthOd of producing interlinkedblades for use in fabricating a blower ,wheel of the centrifugal type,

Lwhiehmethod comprises the steps of cutting away portions of both ,endsofa rectangular blank of sheet mahaving a notch in each end ,-ther eof and an end shape ,connectedto each end of the QbOdy PQItlOn ,with,each nd shape including a tab portionhavinga notch thereimbending the tab portion of each end shapein one direction so as to extend away ufrom the plane ofsaid body portion, bending each end hape in said one direction along a transverse line adjacent the associated end of said body portion, and,..dur-

"ing said latter bending operation, positioning said end shapes in such relation to the bodyportion of another blade that the notchesin the tabs of the end shapes being 1 bententer-and interfit-with notches in the respective ends bf the-body portion .of said other blade.

8. .The. method. of producing interlinked blades for use in fabricating a blower wheel of the centrifugal type, which methodcornprisesthesteps of cutting away portions of both ends of a rectangular blank of sheet material'to leave a body portion having a notch in 'each' end thereof and an end shape connected to eachend 'of the body portion with each end shape including a 'tab portion having a notch therein, bending the tab portion of each end shape so as to'eXtend downwardly from the plane of said blade body portion, bending each end shape downwardly along a transverse bend line adjacent .the associated end of said body portion by an angle not more than approximately and with at least one of saide'nd shapes being bent by an anglesubstantially less than 90?, positioning said blank adjacent another blade ihaving notches in each end of its'body portion, and b'ending each'end shape previously bent to an angle of less than 90 to approximately a full 90 to bring the notches of said tabsinto interfitting engagement with the notches in the body portion of said other blade.

9. The method for making a chain of interlinked blades for use in fabricating a blower wheel of' the centrifugal type, which method comprises the steps of providing a -first longitudinal air moving blade having an outwardly opening notch in each end of its body anda flange on each end of its body bent away from the bodyalong a transverse bend line, each of said flanges having a tab on the outer end thereof formed with a generally inwardly opening notch in its inner end, providing a second blade similar to said first blade, and having theinner ends of the tabs on the opposite ends thereof'spaced further apart than the spacing between the notches in the body of said first blade, positioning the tab notches of said second blade in straddling relationship with the body notches of said first blade, bending at least one of thevflanges on said second blade a further distance inwardly along its transverse bend line to decrease the spacing between the opposed tabs and bring the tab notches of said second blade into interlinking relationship with the body notches of said first blade, providing subsequent blades similar to said second blade, and individually connecting each subsequent blade to the next preceding blade by 'the same steps as employed in connecting said second blade tosaid first blade.

10. The method for making a continuous chain of interlinked blades for use in fabricating al'blowei wheel of the centrifugal type, which method comprisesthe steps of providing a first longitudinal 'airmoving bladehavin'g an outwardly opening notch in each end of its'body and a flange on each end of its body bent away .from the body along a transverse bend line, each of said flanges having a tab on the outer end thereof formed with a v generally inwardly opening notch in its inner end, providing a second blade similar to said first blade, positioning the tab notches of said second bladeiin straddling relationship with the body notches of said first blade, bending at least one of the-flanges on said second blade a further distance inwardly along its transverse bendline to decrease the .spacing between the opposed .tabs and bring the tab notches into interlinking relationship with the body notches of said first blade, providing a given number of subsequent blades similar to saidfirst blade,

the flanges on said first blade a further distance inwardly along its transverse bend line to decreasethe spacing between the' opposed tabs and bring the tab notches into interlinking relationship wi'ththebody notches of said last blade. Y v i Y 11. The method for making a blower wheel of the centrifugaltype, which method comprises theste ps of providing a first longitudinal air moving blade having an outwardly opening "notch ineach end of its body and a 9 flange on each end of its body bent away from the body along a transverse bend line, each of said flanges having a tab on the outer end thereof formed with a generally inwardly opening notch in its inner end, providing a second blade similar to said first blade, positioning the tab notches of said second blade in straddling relationship with the body notches of said first blade, bending at least one of the flanges on said second blade a further distance inwardly along its transverse bend line to decrease the spacing between the opposed tabs and bring the tab notches into interlinking relationship with the body notches of said first blade, providing subsequent blades similar to said first blade, individually connecting each subsequent blade to the next preceding blade by the same steps as employed in connecting said second blade to said first blade to provide a length of interlinked blades, providing an annular hub structure rotatable about a central axis, positioning said length of interlinked blades around the periphery of said hub structure with the longitudinal axes of said blades parallel to said central hub axis, connecting the last blade of said length of interlinked blades to said first blade by the same steps as employed in connecting second blade to said first blade, and connecting each blade in fixed relationship to the hub structure.

12. The method for making a blower wheel of the centrifugal type, which method comprises the steps of providing a chain of interlinked blades having elongated arcuate foot portions extending generally outwardly from the ends thereof and elongated arcuate oifset portions each located on the outer edge of a respective one of said foot portions and extending generally perpendicular thereto, closing said chain upon itself by positioning the first blade of said chain adjacent the last blade of said chain, arranging said closed chain into a substantially circular form so that the elongated offset and foot portions of said blades collectively define substantially continuous annuli on the ends of said chain with the foot portions of each end of said chain being located in a common plane, and attaching an end ring to each end of said chain in such a manner that the ring engages both the annulus formed by the associated offset portions and the annulus formed by the associated foot portions to hold said foot portions in their annular relationship and to hold said oifset portions in said common plane.

References Cited in the file of this patent UNITED STATES PATENTS 2,458,041 Wessel Jan. 4, 1949 2,894,681 Lunde et al. July 14, 1949 2,537,805 Wilken Jan. 9, 1951 

1. A BLOWER WHEEL OF THE CENTRIFUGAL TYPE COMPRISING A HUB STRUCTURE ROTATABLE ABOUT A CENTRAL AXIS, A PLURALITY OF LONGITUDIANL AIR MOVING BLADES ROTATABLE WITH SAID HUB STRUCTURE, SAID BLADES BEING ARRANGED IN AN ANNULAR SERIES ABOUT SAID HUB STRUCTURE WITH THE LONGITUDINAL AXES THEREOF GENERALLY PARALLEL TO SAID CENTRAL AXIS AND WITH THE OPPOSITE ENDS OF SAID BLADES DISPOSED RESPECTIVELY IN TWO AXIALLY SPACED RADIAL PLANES, A FLANGE ON EACH END OF EACH BLADE EXTENDING FORWARDLY AND RADIALLY OUTWARDLY WITH RESPECT TO THE ASSOCIATED BLADE, MEANS DEFINING AN AXIALLY OUTWARDLY OPENING NOTCH IN EACH END OF EACH BLADE REARWARDLY OF THE ASSOCIATED FLANGE, AND AN AXIALLY INWARDLY DIRECTED TAB ON THE FORWARD PORTION OF EACH OF SAID FLANGES, EACH OF SAID TABS HAVING AN AXIALLY INWARDLY OPENING NOTCH IN THE INNER END THEREOF WHICH ENGAGES IN INTERFITTING RELATIONSHIP THE NOTCH IN THE CORRESPONDING END OF THE NEXT ADJACENT BLADE TO LINK TOGETHER ADJACENT BLADES AND PREVENT RELATIVE CIRCUMFERENTIAL AND AXIAL DISPLACEMENT THEREBETWEEN. 